48 ON THE USE OF LIME, MARL, AND SHELL-SAND. 



plying lime to the land ; if no effervescence is produced, in all 

 probability liming or marling will be useful. However, this 

 simple test cannot always be depended upon, and it is therefore 

 much safer to have the proportion of lime determined in the 

 soil, which at no great expense can be done by any analytical 

 chemist. 



On the Application of Shell-sand to some Cornish Soils. 



In conclusion, a few remarks on the use of shell-sand in rela- 

 tion to some Cornish soils lately examined by me may not be 

 amiss, since they apply no doubt to many other soils of Cornwall 

 and Devonshire, upon which shell-sand is largely employed as a 

 manure. 



It has been stated already that immense quantities of shell- 

 sand are annually used for agricultural purposes on the coast of 

 Cornwall and Devonshire. A great diversity of opinion appears 

 to prevail amongst practical men as to the economy with \vhirh 

 sea or shell-sand is used by the farmer. Some allege that the 

 effect of sand on the crops is very marked ; others that hardly 

 any effect is seen to follow the application of shell -sand to the 

 land. 



There can be no doubt that in some instances shell-sand does 

 no good, but at the same time it must be admitted that in the 

 majority of cases shell-sand is a useful manure for most soils 

 resting on the clay-slate or granite formations along the Devon- 

 shire and Cornish coast, for these soils are generally very poor in 

 lime. The use of shell-sand, however, like that of many other 

 good things, has been much abused. It is too often forgotten 

 that repeated heavy dressings of sea-sand cannot produce so 

 good effects as the first application, since shell-sand owes its 

 fertilizing qualities almost exclusively to the lime it contains, 

 and it ought to be remembered that no single manuring element 

 can permanently maintain the land in good heart. It is, indeed, 

 plain that the effects which usually follow the first application 

 of sea-sand must cease when the quantity of lime incorporated 

 uniformly with the surface- soil is so large that the spongeoles 

 of the roots can readily find more than sufficient lime to meet 

 all the requirements of the growing plant. 



The examination of some soils from the neighbourhood of 

 Bude has furnished to me, I think, decided proofs that there 

 are many soils in Cornwall which are much benefited by a 

 dressing with shell-sand, and also that shell-sand is often applied 

 to land upon which it is not needed, and upon which money 

 would be far more beneficially spent in the purchase of artificial 

 manures or of artificial food. 



The following Table exhibits the composition of five soils 



